Test interface equipment has been incorporated for some time in telephone entrance panels. In one form, the test interface equipment involves a jack or receptacle to which a line of a distribution network is connected; plug connected to a subscriber's line normal remains in that receptacle and connects the subscriber's line to, the network line. When a test is to be performed using that form of interface, the plug of the subscriber's line is removed from the receptacle as a first step in the test procedure, and a plug of a test device is then inserted into the jack. The test device may be a telephone that is known to be in proper working order. If (and only if) the test device works properly in this test, the network line is known to be in good working condition. Accordingly, the trouble that prompted the test must be in the subscriber's line.
In the interest of simplifying the test and reducing the cost of the interface panel, modified forms of test interface have been developed. In one modified test interface, a switching receptacle is provided which connects the subscriber's line to a network line when the receptacle is empty. When the plug of a test device is inserted into the receptacle, the subscriber's line is disconnected and the receptacle connects the test device to the network line. To be compatible with telephone distribution lines, the receptacle advantageously adopts the standardized configuration used in telephone system practice, as represented by the RJ-11 or RJ-45 configurations mentioned in U.S. Pat. No. 5,030,123, issued Jul. 9, 1991, to Silver.